relatively flat and open areas with exposed soil and rock substrates with short, widely spaced forbs and grasses above 8,200 ft, but isolated individuals have been observed as low as 6,500 ft of the Spring Mountains, located approximately 25 miles west of Las Vegas in Clark County, Nevada

Official Status:

Endangered, 10/21/2013

Life History:

The Mount Charleston blue butterfly is presumed to diapause (period of suspended growth or development similar to hibernation) at the base of the larval host plant or in the surrounding substrate as an egg the first year, a larva the second year, and is suspected of having additional diapause during unfavorable years. Adults live one season, typically a short span of time (< 1 or 2 weeks) during the known flight or breeding period. The typical flight and breeding period for the butterfly is early July to mid-August with a peak in late July, although the species has been observed as early as mid-June and as late as mid-September.

Like most butterfly species, the Mount Charleston blue butterfly is dependent on plants both during larval development (larval host plants) and the adult butterfly flight period (nectar plants). The Mount Charleston blue butterfly requires areas that support one or more of its larval host plants which includes Torrey’s milkvetch (Astragalus calycosus var. calycosus), mountain oxytrope (Oxytropis oreophila var. oreophila), and broad-keeled milkvetch (Astragalus platytropis). Its primary nectar plants are Clokey's fleabane (Erigeron clokeyi), Lemmon bitterweed (Hymenoxys lemmonii), Cooper rubberweed (Hymenoxys cooperi), and sulphur-flower buckwheat (Eriogonum umbellatum var. versicolor), however it has also been observed to use other species for nectar.

The wingspan of the Mount Charleston blue butterfly ranges from ¾ to 1 inch. Males are dark to dull iridescent blue and females are brown with a blue overlay. Their underside is gray, with a pattern of black spots, brown blotches and pale wing veins to give it a mottled appearance.

Distribution and Habitat:

The Mount Charleston blue butterfly is a distinctive subspecies of the wider ranging Shasta blue butterfly (Icaricia (Plebejus) shasta), a member of the Lycaenidae family. The subspecies is known to occur only at high elevations of the Spring Mountains, located approximately 25 miles west of Las Vegas in Clark County, Nevada. The butterfly requires open habitat that supports its larval host plants, which grow between 8,200 to 11,500 feet in the Spring Mountains. Populations of the Mount Charleston blue butterfly are located within and adjacent to Kyle and Lee Canyons, on lands managed by the Forest Service in the Spring Mountains National Recreation Area of the Humboldt-Toiyabe National Forest.

Threats:

Threats and conservation issues to the Mount Charleston blue butterfly include: loss and degradation of habitat due to changes in natural fire regimes and succession; the implementation of recreational development projects and fuels reduction projects; and the increases in nonnative plants will increase the inherent risk of extinction of the remaining few occurrences of the Mount Charleston blue butterfly. These threats are likely to be exacerbated by the impact of climate change, which is anticipated to increase drought and extreme precipitation events.